This invention relates generally to packet networks and more particularly to a packet network that supports packet header suppression and multiple microflows on the same Service Identification field.
A voice or other type of data stream is transmitted over a packet network by first formatting the data stream into multiple discrete packets. For example, in a Voice over Internet Protocol (VoIP) application, a digitized audio stream is quantized into packets that are placed onto a packet network and routed to a packet telephony receiver. The receiver converts the packets back into a continuous digital audio stream that resembles the input audio stream. A codec (a compression/decompression algorithm) is used to reduce the communication bandwidth required for transmitting the audio packets over the network.
A large amount of network bandwidth is used for overhead when a data steam is converted and transmitted as packets. Voice packets have a certain length according to recording time. Typical recording times are usually 10 or 20 milliseconds. Sending packets with longer recording times increase bandwidth efficiency by reducing the percentage of the packet used for overhead and increase the percentage of the packet used for voice payload. The disadvantage of transmitting packets with more voice payload is that the packets have more latency. Thus, for better performance, smaller voice packets (10 ms) are transmitted that each have a higher percentage of packet overhead. The large amount of network bandwidth used for packet overhead reduces the maximum number of connections that can be established on the network.
Cable modem networks are used to carry VoIP packets and other data between a cable modem termination system and multiple cable modems. The cable modems are identified using a Service Identification (SID) field. The cable modems may carry a diverse amount of traffic, both originating from internal ports and from external ports. Each unique combination of source and destination addresses and ports is referred to as a microflow. The number of SIDs assigned to the cable modem may be limited, either due to hardware limitations or network provisioning limitations. As a result, the number of microflows can exceed the number of available SIDs.
Accordingly, a need remains for a system that more efficiently uses bandwidth in a packet network and can also assign multiple microflows to the same Service Identification field.